Predicting muscle activation patterns from motion and anatomy: modelling the skull ofSphenodon(Diapsida: Rhynchocephalia)

Abstract

The relationship between skull shape and the forces generated during feeding is currently under widespread scrutiny and increasingly involves the use of computer simulations such as finite element analysis. The computer models used to represent skulls are often based on computed tomography data and thus are structurally accurate; however, correctly representing muscular loading during food reduction remains a major problem. Here, we present a novel approach for predicting the forces and activation patterns of muscles and muscle groups based on their known anatomical orientation (line of action). The work was carried out for the lizard-like reptile Sphenodon (Rhynchocephalia) using a sophisticated computer-based model and multi-body dynamics analysis. The model suggests that specific muscle groups control specific motions, and that during certain times in the bite cycle some muscles are highly active whereas others are inactive. The predictions of muscle activity closely correspond to data previously recorded from live Sphenodon using electromyography. Apparent exceptions can be explained by variations in food resistance, food size, food position and lower jaw motions. This approach shows considerable promise in advancing detailed functional models of food acquisition and reduction, and for use in other musculoskeletal systems where no experimental determination of muscle activity is possible, such as in rare, endangered or extinct species.

Bite‐force performance of the last rhynchocephalian (Lepidosauria:Sphenodon)

“…This dynamic behaviour of the jaw joint and symphysis may impose a biomechanical constraint that compromises bite force. Computer models of the Sphenodon feeding apparatus are in development (e.g., Curtis et al 2009), with the goal of determining the effects of individual anatomical features on skull biomechanics, performance and, ultimately, related aspects of the behavioural ecology of this unique taxon.…”

A Sensitivity Analysis to the Role of the Fronto‐Parietal Suture in Lacerta Bilineata: A Preliminary Finite Element Study

“…Therefore, varying the properties of the sutures had more of an impact on the anterior regions than the posterior regions (considering the movement across the FP suture). This observation highlights the importance of applying physiological loading conditions to the skull where muscle forces and joint forces would be expected (Duda et al, 1998;Curtis et al, 2008Curtis et al, , 2010Moazen et al, 2008a,b).…”

Coupling finite element analysis and multibody system dynamics for biological research

“…Uncoupled analysis of MDA and FEA have been used before to estimate forces acting on a skull and then applied to a Finite Element Model of this same skull to obtain patterns of strain and stress across it (Moazen et al, 2008a(Moazen et al, , 2008b(Moazen et al, , 2009a(Moazen et al, , 2009bCurtis et al 2008Curtis et al , 2010aCurtis et al , 2010bCurtis et al , 2011. Those results have been combined with knowledge of evolutionary paths to develop hypotheses regarding the genetic and epigenetic factors that shape the skeleton or the feeding mechanism in vertebrate structures.…”

“…It is important to differentiate the FMSD, which couples the equations of the MSD and the FEA during the simulation from the other excellent approaches that can be found in the literature. Firstly, in Curtis et al (2009Curtis et al ( , 2010a, Bates and Falkingham (2012) and Snively et al (2013) only the MSD equations are used to determine the forces that are acting in the model without any interaction with FEA and secondly, in Moazen et al (2008a) and Curtis et al (2011) there is a combination between MSD and FEA but they are not coupled during the simulation. Uncoupled analysis does not account for strains being a result of dynamics response of a flexible object.…”

“…The technique has been applied to studies of craniofacial form to simulate musculoskeletal function and facilitates in-depth exploration of the relationships between musculoskeletal geometry, muscle parameters, forces and motion in vertebrate structures (Curtis et al, 2009;Bates and Falkingham, 2012;Gröning et al, 2013;Snively et al, 2013). In spite of it, the research utilizing both the musculoskeletal modeling and deformable body modeling together has rarely been seen in publications (Moazen et al, 2008a(Moazen et al, , 2008bCurtis, 2011;Curtis et al, 2010aCurtis et al, , 2010bCurtis et al, , 2011. The current research utilizes the flexible multibody dynamics, which is mostly employed in the field of machine dynamics.…”